Finger pump type atomizers for dispensing a spray of liquid have been known in the prior art. They are widely used for dispensing liquids from containers, such as window cleaning preparations, air fresheners, and the like. However, in order to reduce the cost of such finger pump atomizers, it has been the conventional practice to use so-called mechanical break-up atomizing means. These are normally very simple nozzle structures, which, unless the fluid supplied thereto is at sufficient pressure, do not do a very good job of atomizing the liquid.
The finger pump atomizers according to the prior art generally provide pressure on the liquid to be dispensed only when the device is actuated by finger pressure. Unless the device is properly actuated, insufficient pressure is generated and the spray will not be properly atomized at the start or at the end of the dispensing operation, and under the most unfavorable conditions, the spray will be unsatisfactory throughout the actuation of the device.
In order to overcome this problem, there has been proposed in U.S. Pat. No. 3,399,836 a finger pump atomizer in which the parts are arranged to start the dispensing of the liquid only after pressure has been built up during the stroke of the pump plunger. Spring means and a piston are provided within the pump atomizer structure for exerting pressure on the liquid to be dispensed, in combination with the pressure exerted by the movement of the pump plunger.
However, this device is relatively complicated, particularly with respect to the valving for the release of the liquid under pressure after the pressure has been built up. Other dispenser, such as those shown in U.S. Pat. Nos. 3,746,260 and 3,923,250, have spring loaded pistons with elongated valve members thereon extending into the nozzle of the dispenser to keep the nozzle closed until pressure of the liquid to be dispensed acting on the piston withdraws the elongated valve member from the nozzle. When the pressure falls, the spring urges the piston toward the nozzle to close the nozzle. While these dispensers avoid some of the drawbacks of the more complicated device, they still have the drawback that a valve member must be provided on the piston, and the piston must reciprocate substantially in line with the nozzle. Moreover, the above-described devices will dispense liquid only at the time of depression of the pump plunger. They are not able to maintain pressure on the liquid drawn out of the reservoir of liquid to be dispensed, so as to continue dispensing the liquid even, after the pump plunger has been actuated quickly a number of times, when the pump plunger is returning to its initial position to start the next stroke. Only one quantity of the liquid can be dispensed for each depression of the plunger knob.
It would be a distinct advance in the art to have a finger pump atomizer which would start dispensing of the liquid only after a predetermined pressure has been built up on the liquid and would cut off dispensing of the liquid after the pressure falls below the predetermined pressure, yet which is a relatively simple and inexpensive device to build and in which the cutoff member does not have to reciprocate in alignment with the nozzle. Further technical progress in the art would be achieved by the provision of such a finger pump atomizer which could be modified so as to continue to dispense a spray of liquid after one actuation of the plunger has been completed and until the plunger has recovered and can be actuated again.